Currently, within integrated circuits, there exist controllable capacitive devices in the form of micro-electro-mechanical systems (or MEMS). In this regard, the article by DeReus et al. may be cited. This article is entitled “Tunable capacitor series/shunt design for integrated tunable wireless front end applications”, MEMS 2011, Cancun, Mexico, 23-27 Jan. 2011, 2011 IEEE.
The capacitive device described in this article is based on a structure of the suspended bridge type comprising a metal membrane disposed at a distance from a lower electrode underneath a dielectric layer. When the membrane is at a distance from the dielectric layer, the capacitive device exhibits a first capacitive value, which is typically low. Whereas, when the membrane is actuated in such a manner as to come into contact with the dielectric layer, the metal membrane/dielectric layer/lower electrode assembly forms a capacitor having a second capacitive value, which is typically high.
The control of the flexing of the metal membrane is carried out by applying a high voltage, typically of around 50 volts, in such a manner as to provide both a correct flexing of the mobile electrode and to ensure a correct contact with the dielectric layer.
Quite apart from the fact that the technology used to fabricate such devices is a dedicated technology which is difficult to integrate into a standard CMOS process line, the necessity of applying a high voltage, of the order of several tens of volts, is a major drawback. Furthermore, the dielectric layer of the capacitor is, by construction, subjected to high stresses because the mobile electrode hits against the dielectric layer during each movement.